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Wong" , Theodore Ts'o , Alexander Viro , Miklos Szeredi , Andrew Morton , Chaitanya Kulkarni , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, LKML References: <20220225085025.3052894-1-jhubbard@nvidia.com> <20220225120522.6qctxigvowpnehxl@quack3.lan> From: John Hubbard In-Reply-To: <20220225120522.6qctxigvowpnehxl@quack3.lan> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SJ0PR05CA0047.namprd05.prod.outlook.com (2603:10b6:a03:33f::22) To BY5PR12MB4130.namprd12.prod.outlook.com (2603:10b6:a03:20b::16) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 1a7ccdf0-d6b8-447e-18cc-08d9f89621ac X-MS-TrafficTypeDiagnostic: DM5PR12MB1723:EE_ X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BY5PR12MB4130.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230001)(4636009)(366004)(54906003)(6916009)(26005)(186003)(2616005)(38100700002)(6486002)(508600001)(7416002)(5660300002)(6512007)(8936002)(53546011)(6666004)(6506007)(86362001)(66556008)(31686004)(66476007)(66946007)(316002)(2906002)(83380400001)(31696002)(8676002)(4326008)(36756003)(45980500001)(43740500002);DIR:OUT;SFP:1101; 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dkim=pass header.d=Nvidia.com header.s=selector2 header.b=qt2mKr4x; dmarc=pass (policy=reject) header.from=nvidia.com; spf=none (imf28.hostedemail.com: domain of jhubbard@nvidia.com has no SPF policy when checking 40.107.94.71) smtp.mailfrom=jhubbard@nvidia.com X-HE-Tag: 1645830823-177912 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2/25/22 04:05, Jan Kara wrote: ... >> After quite some time exploring and consulting with people as well, it >> is clear that this cannot be done in just one patchset. That's because, >> not only is this large and time-consuming (for example, Chaitanya >> Kulkarni's first reaction, after looking into the details, was, "convert >> the remaining filesystems to use iomap, *then* convert to FOLL_PIN..."), >> but it is also spread across many filesystems. > > With having modified fs/direct-io.c and fs/iomap/direct-io.c which > filesystems do you know are missing conversion? Or is it that you just want > to make sure with audit everything is fine? The only fs I could find > unconverted by your changes is ceph. Am I missing something? > > Honza There are a few more filesystems that call iov_iter_get_pages() or iov_iter_get_pages_alloc(), plus networking things as well, plus some others that are hard to categorize, such as vhost. So we have: * ceph * rds * cifs * p9 * net: __zerocopy_sg_from_iter(), tls_setup_from_iter(), * crypto: af_alg_make_sg() (maybe N/A) * vmsplice() (as David Hildenbrand mentioned) * vhost: vhost_scsi_map_to_sgl() In addition to that, I was also worried that maybe the blockdev_direct_IO() or iomap filesystems might be breaking encapsulation occasionally, by calling put_page() on the direct IO user page buffer. Perhaps in error paths. Are you pretty sure that that last concern is not valid? That would be a welcome bit of news. thanks, -- John Hubbard NVIDIA